Distribution of rDNA and polyploidy in Deschampsia antarctica E. Desv. in Antarctic and Patagonic populations

Abstract

Unlike the Arctic flora, with many flowering plant species offering opportunities to study evolutionary processes, the Antarctic flora offers only two. One of them is the Antarctic grass Deschampsia antarctica E. Desv., whose distribution spans from northern Patagonia (ca. 38°S) down to Alamode Island (ca. 68°S), in the west side of the Antarctic Peninsula. While some aspects of Antarctic plants have been extensively studied (e.g., anatomy, physiology, genetics), little is known about the related Patagonian populations. Particularly in cytogenetics, no single study has focused on continental populations and its relationships with the Antarctic plants. The combination of traditional fluorescent in situ hybridization (FISH) with a phylogenetic framework highlights the importance of cytogenetics in plant evolutionary studies, by allowing comparison of chromosome characters in phylogenetically related individuals. Most used characters for this purpose are the chromosome number, karyotype morphology and patterns of repetitive DNA. These were used to compare distant populations of D. antarctica in a phylogenetic framework, to obtain a first view of the cytogenetic structure of the species along its distribution. Patagonian populations have greater variability in the chromosomal and molecular characters, while Antarctic populations are very alike, hinting at a South American origin hypothesis. A polyploid population is reported for the first time, located on Central Patagonia populations, close to the northern limit of distribution range. Cytogenetic characteristics suggest that hybridization processes could have played an important role in the evolution of the genome of D. antarctica.